如何在Golang中实现多线程文件下载_Golang 多线程文件下载实践

resp, err := http.Head(url)
if err != nil || resp.StatusCode != 200 {
    log.Fatal("不支持下载或无法获取文件信息")
}
if resp.Header.Get("Accept-Ranges") != "bytes" {
    log.Fatal("服务器不支持分块下载")
}
fileSize := resp.ContentLength

const numWorkers = 4
const numChunks = 10
<p>var wg sync.WaitGroup
sem := make(chan struct{}, numWorkers) // 控制并发</p><p>for i := 0; i < numChunks; i++ {
start := fileSize <em> i / numChunks
end := fileSize </em> (i+1) / numChunks - 1
if i == numChunks-1 {
end = fileSize - 1 // 最后一块包含剩余字节
}</p><pre class="brush:php;toolbar:false;"><pre class="brush:php;toolbar:false;">wg.Add(1)
go func(partID int, start, end int64) {
    defer wg.Done()
    sem <- struct{}{} // 获取信号量
    defer func() { <-sem }()

    downloadChunk(url, partID, start, end)
}(i, start, end)

func downloadChunk(url string, partID int, start, end int64) error {
    client := &http.Client{}
    req, _ := http.NewRequest("GET", url, nil)
    req.Header.Set("Range", fmt.Sprintf("bytes=%d-%d", start, end))
<pre class="brush:php;toolbar:false;"><pre class="brush:php;toolbar:false;">resp, err := client.Do(req)
if err != nil || resp.StatusCode > 299 {
    return fmt.Errorf("下载失败: %v", err)
}
defer resp.Body.Close()

file, err := os.Create(fmt.Sprintf("file.part%d", partID))
if err != nil {
    return err
}
defer file.Close()

io.Copy(file, resp.Body)
return nil

outFile, _ := os.Create("output.file")
defer outFile.Close()
<p>for i := 0; i < numChunks; i++ {
partFile, _ := os.Open(fmt.Sprintf("file.part%d", i))
io.Copy(outFile, partFile)
partFile.Close()
os.Remove(fmt.Sprintf("file.part%d", i)) // 删除临时文件
}

for i := 0; i < 3; i++ {
    err := downloadChunk(...)
    if err == nil {
        break
    }
    time.Sleep(time.Second << i) // 指数退避
}